Interpretive Summary: Highly pathogenic avian influenza (HPAI), the deadly form of avian influenza in birds, is typically eradicated by depopulation programs. However, vaccine has been used as a control measure in a limited number of outbreaks. Over 113 billion doses have been used in poultry, mostly in China, Egypt, Indonesia and Vietnam, where vaccination of poultry is routine. Nine other countries have vaccinated, but have stopped. H5N1 HPAI has occurred in countries that vaccinate poultry because of vaccine failures, but more commonly these problems have resulted from the inability to catch and inject all the poultry in the country.

Technical Abstract:
Thirty epizootics of high pathogenicity avian influenza (HPAI) have occurred in the world since influenza was identified as the etiology in 1955. Twenty-four of the epizootics were eradicated by using stamping-out programs composed of education, biosecurity, rapid diagnostics and surveillance, and elimination of infected birds. Four epizootics used vaccines and vaccination as an adjunct to stamping-out strategies; three of these four have eradicated HPAI. Two recent HPAI epizootics are nearing eradication without use of vaccines. The ability to eradicate HPAI is influenced by the competency of the governmental veterinary medical authority, density of poultry within the country, and the level of governmental participation. The largest epizootic, a panzootic, is the H5N1 HPAI that has infected poultry and/or wild birds in 63 countries since the first reported cases in Guangdong China during 1996. Vaccine has been used in 13 of the 63 countries. From all HPAI epizootics from 2002-2010, >113 billion doses of AI vaccine were used in poultry, primarily against H5N1 HPAI but small amounts against H7N3 and H7N7 HPAI. The majority of vaccine has been used in four H5N1 HPAI enzootic countries of China (91%), Egypt (4.7%), Indonesia (2.3%), and Vietnam (1.4%). Implementation of vaccination occurred in these four countries after H5N1 HPAI became enzootic. The other nine H5N1 HPAI affected countries used less than 0.7% of the vaccine in a targeted approach as a preventative measures, or against quickly controlled outbreaks in a targeted approach. Inactivated AI vaccines accounted for 95.5% and live recombinant virus vaccines for 4.5% of vaccine used. Field outbreaks of HPAI have occurred in countries that vaccinate poultry as the result of either vaccine failure or improperly administration to the target species. Antigenic drift in field viruses has resulted in failure to protect by classic H5 vaccines strains in Mexico, China, Egypt, Indonesia, Hong Kong and Vietnam, but the major reason for failures have been logistic; i.e. not enough poultry being vaccinated to produce population immunity. The following would improve the vaccines and vaccination to control HPAI: 1) restructuring and modernization of veterinary services; 2) improving national HPAI surveillance programs; 3) restructuring funding for H5N1 HPAI control; 4) improving vaccination rates among domestic ducks; 5) developing new vaccine vector platforms; 6) continuing development of antigenically-relevant reverse genetic AI seed strains; and 7) developing a more time-responsive vaccine licensing and registration process.